Precipitator



Aug. 6, 1935. c. c. LEVY PRECIPITATOR Filed Feb. 14, 1934 7c3fnerya zed Source INVENTOR WITNESSES Patented Aug. 6, 1935 UNITED STATES.

PRECIPITATOR Cyril C. Levy, Pittsburgh, Pa., assignor to Westinghouse Electric 8; Manufacturing Company,

East Pittsburgh, Pa, a corporation of Pennsylvania Application February 14, 1934, Serial No. 711,191

8 Claims. (01. 133-7) The invention relates generally tosystems for the precipitation of solid particles from gases and more particularly to the controlling of the current supplied for performing the precipitating 5 process.

It has been found that when the charging circuits of the precipitating system are connected directly to a source of supply that the system does not readily re-establish normal precipitating conditions after a fiashover. Expedients, such as connecting a resistor in series circuit relation with the charging system, have been resorted to, but this results in a considerable power loss.

The object of the invention is to provide for impressing a voltage on the ionizing electrode of a precipitation system with a small power loss during the normal ionizing process and for momentarily reducing the voltage impressed on the electrode when a fiashover occurs to enable the system to re-establish normal operating conditions.

It is also an object of the invention to provide for utilizing changes in the voltage conditions at the electrode of a precipitation system for controlling the voltage impressed on the electrode.

Other objects of the invention will, in part, be obvious and, in part, appear hereinafter.

The invention accordingly is disclosed in the embodiment thereof shown in the accompanying drawing, and comprises the features of construction, combination of elements and arrangement of parts which will be exemplified in the system hereinafter set forth, and the scope of the application of which will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference maybe had to the following detailed description taken in connection with the accompanying drawing, in which the figure is a diagrammatic view of a precipitation system arranged in accordance with this invention.

In order to reduce the smoke nuisance in the, vicinity of large industries and in some instances to recover valuable products from smoke and gases, precipitation systems have been employed. In industries, such as the manufacture of iron and steel, the gases from blast furnaces are cleansed in order that they may be utilized for operating internal combustion engines.

Referring to the drawing, the reference character Ill designates generally a smoke stack or pipe through which gases containing solid particles are conveyed. As illustrated, the stack or pipe I is grounded at H. The ground connection may be made in any suitable manner well known in the art. f o

A wire or electrode I2 is disposed in the pipe or stack ID to receive a negative ionizing potential or voltage. The electrode l2, as illustrated. is connected to the plates of the rectifying tubes l3 and I4.

' The negative potential for the electrode |2 may be drawn from any suitable source of power and in this instance a transformer I5 is provided. As shown, the transformer I5 is provided with secondary coils l6 and I! which are connected to the filaments of the tubes l3 and It, respectively. The filaments of the rectifier tubes l3 and It may be heated by transformers 36 and 3! respectively which in turn are connected to a suitable power source.

The primary winding |8- of the transformer I5 is supplied from a source of alternating current power I 9, which in this instance is a transmission system.

In order to supply an alternating potential to the transformer 5 with a-small loss of power, two three-electrode electronic tubes 20 and 2| are connected between the power source l9 andone terminal of the primary winding l8 of the transformer l5. 1

As illustrated, tertiary windings 22 and 23 are provided in the transformer l5 for impressing a voltage on the grids of the tubes 20 and 2| to control the flow of current. Interposed between the tertiary windings 22 and 23 and the grids of their corresponding tubes are variable resistors 24 and 25, respectively for changing as desired the voltage impressed on the grids.

In order to heat the filaments of the electronic tubes 20 and 2|, small transformers 26 and 21 are provided. As shown, the primaries of these transformers are connected across the power source |9, while the secondaries are connected across the filaments.

A reactor 28 is connected in parallel circuit relation with the electronic tubes 20 and 2| to deliver current to one terminal of the primary winding of the transformer ii. The reactor 28 will be designed to meet the conditions existing in the particular system to which it is to be applied.

In the operation of the precipitation system when the ionizing process is being carried on normally the electrode I2 is charged through the rectifying tubes 3 and I 4 at a predetermined voltage from the transformer I5. The voltage conditions in the transformer remain substantially constant as long as the charging operation continues without flashovers or short circuits.

As is well known in the operation of electronic tubes, the resistance ofiered to the flow of current may be controlled by the voltage impressed on the grid! In this instance, when a predetermined voltage is impressed on the electrode l2 the variable resistors 24! and 25 are adjusted to impress the proper voltage on the grids of the tubes 20 and M, respectively, to permit current to flow thrOugh the tubes to one terminal of the transformer I5 with a minimum power loss.

When the voltage impressed on the electrode I2 stands at the predetermined value required for performing the precipitating process the transformer I5 is supplied with power from the power source -I 9 through the electronic tubes 20 and 2 I. The transformer circuit through the tube 20 extends from one side of the power source I9 through conductors 29 and 30, the plate and filament of the electronic tube 20, conductors SI and 32, the primary coil I8 of the transformer i5 and conductor 33 to the other side of the power source. Power is supplied to the transformer for one-half of the cycle through this circuit.

Another transformer circuit connected in parallel circuit relation to the tube 20 extends from the energized conductor 29 through conductor 36, the filament and plate of the electronic tube 2I, conductors 35 and 32 and the primary coil of the transformer I5 to the power source I9. This circuit provides for the supplying of current during the other half of the cycle. Thus, current is supplied continuously to the transformer is through the electronic tubes 20 and M from the alternating-current source I9 when the charging operation is proceeding normally.

Assuming that a fiashover occurs at the electrode I2, then voltage. conditions at the electrode I 2 will vary greatly, causing a change in the voltage conditions in the transformer l5. In this manner the voltages impressed on the grids of the electronic tubes 20 and 2! are changed in response to variations in potential conditions at the electrode l2,with the result that the tubes offer high resistance to the flow of current. In fact, the electronic tubes may be so designed that they will act as valves and interrupt the flow of current through the supply circuits in which they are connected.

The supply of power through the electronic tubes 26 and iii is interrupted on the occurrence of abnormal potential or voltage conditions at the electrode I2, but the transformer is still connected across the power source I9. The transformer circuit extends from the one side of the power source through conductor 29, reactor 28, conductor 32, the primary coil I8 of the transformer l5 and conductor 33 back to the power source.

When the electronic tubes 20 and 2! function to interrupt the supply of power through the circuits in which they are connected, the primary of the transformer I5 is connected across the power source through'the reactor 28. The result is that the voltage drop across the reactor 28 momentarily greatly reduces the voltage applied across the primary of the transformer l5, and the voltage impressed on the electrode I2 is reduced to the point where it will not maintain an arc established by a flashover. As soon as the arc is interrupted, a deionizing process will take place at the surface of the electrode and normal volt age conditions will be established and the precipitating process will proceed.

From the foregoing it will be clear that there is a very small loss of power in the system during normal operations but upon the occurrence of abnormal voltage conditions the flow of current is restricted until normal voltage conditions at the ionizing electrode are re-established. In this manner high efficiency and simplicity in operation are obtained.

Since certain changes may be made in the above system, and different embodiments of the invention could be made without departing from the scope thereof, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

I claim as my invention:

1. A precipitation system comprising, in combination,- an electrode, means for impressing a unidirectional potential on the electrode, means responsive to predetermined voltage conditions at the electrode for conducting current to the potential impressing means, and means independent of the voltage conditions at the electrode for controlling the voltage impressed on the electrode, said independent means being capable of limiting the flow of current.

2. A precipitation system comprising, in combination, an electrode, a source of power, means connected to the source of power for impressing a potential on the electrode to carry on a process of precipitation, means interposed between the source of power and the means for impressing a potential on the electrode for conducting current, said current conducting means being responsive to the voltage conditions at the electrode, and means for conducting current from the source of power to the means for impressing a potential on the electrode, said last mentioned conducting means being non-responsive to the voltage conditions at the electrode and capable of momentarily greatly reducing the voltage impressed on the electrode.

3. A precipitation system comprising, in combination, an electrode, a source of power, means connected to the source of power for impressing a potential on the electrode to carry on a process of precipitation, means interposed between the source of power and the means for impressing a potential on the electrode for conducting current, said conducting means being responsive to the voltage conditions at the electrode, and means for conducting current from the source of power to the means for impressing a potential on the electrode, said conducting means being non-responsive to the voltageconditions at the electrode and capable of momentarily greatly reducing the voltage impressed on the electrode, the current conducting means responsive to the voltage conditions at the electrode and the current conducting means not responsive to the voltage conditions at the electrode'connected in parallel circuit relation.

4. A precipitation system comprising, in combination, an electrode, a source of power, means connected to the source of power for impressing a voltage on the electrode to perform the precipitating process, the means for impressing the voltage on the electrode being connected to the source of power through a plurality of parallel circuits, means responsive to voltage conditions at the electrode connected into some of the circuits for controlling the flow of current, and means not responsive to the voltage conditions at the electrode connected into the other parallel connected circuits, said non-responsive means being capable of greatly reducing momentarily the voltage impressed upon the electrode.

5. A precipitation system comprising, in combination, an electrode, a source of power, means connected to the source of power for impressing a voltage on the electrode to perform the precipitating process, the means for impressing the voltage on the electrode being connected to the source of power through a plurality of parallel .circuits, means responsive to voltage conditions at the. electrode connected into a plurality of the circuits for controlling the flow of current, and means not responsive to the voltage conditions at the electrode connected into the other parallel connected circuits, said non-responsive means bevoltage impressing means, conducting circuits.

connected between the source of power and the charging means, said conducting circuits being responsive to the voltage conditions at the electrode to offer small resistance to the flow of current when the voltage impressed upon the electrode is that required for normal precipitating operation and for greatly reducing momentarily the voltage impressed on the electrode when a flashover occurs.

7. A precipitation system comprising, in combination, an electrode, means for impressing a voltage on the electrode to perform a precipitating process, a source of power for supplying power to the means for impressing avoltage on the electrode, a low resistance voltage controlled conducting circuit interposed between the source of power and the means for impressing a voltage on the electrode, the conductance of the circuit being controlled by the voltage at the electrode, and a reactance connected in parallel circuit relation with the low resistance circuit, said reactance being non-responsive to the voltage conditions at the -electrode and capable of greatly reducing momentarily the'voltage impressed upon the electrode when the fiashover occurs disturbing the voltage conditions at the electrode and effecting the low resistance circuits.

8. A precipitating system comprising, in combination, an electrode, means for impressing the voltage on the electrode to perform a precipitating process,. a source of power for supplying the CYRIL 'C. LEVY. 

